**3.7 Gold hydroxide solution**

For the shell growth process, a gold hydroxide solution was prepared by mixing 100 ml of 2 mM K2CO3 solution and 1.5 ml of 1% HAuCl4 in a 140 ml glass flask for

**93**

**Figure 4.**

*yellow) and (b) 30 min of reaction (transparent).*

*A Simple Way to Produce Gold Nanoshells for Cancer Therapy*

30 min. The color of the solution changed from light yellow (**Figure 4a**) to transparent (**Figure 4b**). It was left still overnight at room temperature in an amber glass

The shell was developed from the gold seeds deposited over the functionalized silica particles with the help of the Au(OH)4¯ ions. About 100 ml of the gold hydroxide solution (**Figure 5a**) and 5 ml of seeded silica were magnetically stirred in a 140 ml glass flask for 5 min (**Figure 5b**). Next, 5 ml of formaldehyde was added to the solution (**Figure 5c**) and stirred for 10 min (**Figure 5d**). The solution was left still for 50 min. Finally, it was centrifuged at 6000 rpm for 2 min, washed, and

*Images illustrating the change of color of the gold hydroxide solution at (a) the beginning of the synthesis (light* 

bottle to facilitate the formation of Au(OH)4¯ ions [18].

*Images at (a) the beginning of the seeding process and (b) after 2 h of resting time.*

dispersed in 10 ml of deionized water final volume.

**3.8 Shell growth**

**Figure 3.**

*DOI: http://dx.doi.org/10.5772/intechopen.82495*

**Figure 2.** *Synthesis of GNPs at (a) the beginning of the reaction and (b) after 10 min of reaction.*

*A Simple Way to Produce Gold Nanoshells for Cancer Therapy DOI: http://dx.doi.org/10.5772/intechopen.82495*

**Figure 3.** *Images at (a) the beginning of the seeding process and (b) after 2 h of resting time.*

30 min. The color of the solution changed from light yellow (**Figure 4a**) to transparent (**Figure 4b**). It was left still overnight at room temperature in an amber glass bottle to facilitate the formation of Au(OH)4¯ ions [18].
